Physicochemical characterization, identification and improved photo-stability of alpha-lipoic acid-loaded nanostructured lipid carrier

Objective: The ultimate goal of this research is to corroborate the physicochemical characterization of nanostructured lipid carrier (NLC) loading unstable lipophilic active ingredients with an antioxidant function, such as alpha-lipoic acid (ALA), and monitoring its photochemical stability of ALA-NLC against natural daylight. NLC is an innovative active compound delivery system in pharmaceutical and cosmetic fields. It has been recommended as active substance carriers to enhance the effectiveness of lipophilic compounds. Methods: ALA-NLC was manufactured using hot high pressure homogenization technique to increase the water solubility and photo-stability. The physicochemical characterization properties of ALA-NLC have been determined in terms of nanoparticle size, zeta potential, polydispersity index value and size distribution. Size analysis was implemented through photon correlation spectroscopy and laser diffractometry. Morphological profile of nanoparticles was observed via atomic force microscopy. The loading of NLC containing ALA was evaluated by high performance liquid chromatography. ALA-NLC was subjected to UV-Vis spectrophotometer to validate the existence of ALA. Water contact angle measurement was manipulated to determine the hydrophilicity of the sample. The photo-stability of ALA-NLC within 120 days was assessed by the retention of ALA. Results: The ALA-NLC provided maximum ALA retention of 93.9% in 30 days exposure to natural daylight, the retention of free ALA only 42.5%. About 88.5% of the initial ALA in NLC system remained after 120 days under the same conditions, while the retention of free ALA only 0.7% under natural daylight irradiation. The photo-stability of ALA was considerably enhanced by NLC formulation compared with free ALA itself. Therefore, the NLC formulation provided a reliable protection of ALA against natural daylight, enhancing its photochemical stability. Conclusion: The present investigation elucidated that the NLC drastically improved the water solubility, particularly the facilitation of photo-stability of ALA exposure to natural daylight.